No. Science has confirmed that Vince was prescient. He also advocated a low-carbohydrate diet, and we now know that restricting carbs turns the body from a sugar-burning machine to a fat-burning machine, the result being that you not only tap into bodyfat stores but also oxidize, or burn, fat more rapidly.
Vince had observed that polyunsaturated fat seemed linked to a greater use of bodyfat as fuel for exercise. Recent studies have confirmed that and have found that polyunsaturated fat can turn off fat-synthesizing genes in the body, though some forms are better at it than others.Omega-6 fats, found in various vegetable oils, qualify as polyunsaturated fats. Linoleic acid, for example, is one of two essential fatty acids, meaning that the body cannot synthesize it and must get it from food. Enzymes convert linoleic acid into arachidonic acid, which is trouble because that’s the major substrate for eicosanoids, substances that are potent inflammatories. Out-of-control inflammation is now recognized as the underlying cause of most degenerative disease, such as cardiovascular disease and cancer. Clearly, taking large doses of omega-6 fats to speed bodyfat loss is a nonstarter, unless you’re interested in a slow, painful death.
Omega-3 fats, the other essential fatty acids, are present in fish oil and are quite another matter. They suppress inflammation and offer many other health benefits. The question is, Do they help you lose bodyfat? Animal studies show that taking in a lot of omega-3 fat blunts bodyfat synthesis, even when you eat a lot of saturated fat, which is ordinarily associated with insulin resistance and bodyfat gain.
Another type of fat, conjugated linoleic acid, encourages fat loss in rodents and other animals, but the effect in humans isn’t as clear. Among the various isomers of CLA, only one kind can induce fat loss.In terms of their influence on fat loss, omega-3 fats are nearly as controversial as CLA. A recent study provided a generous dose of fish oil supplements to eight healthy young men, average age 24, whose average bodyfat level was 19 percent and who were engaged in exercise.1 Some of them took 7.2 grams a day of a fish oil supplement while others took nothing for 14 days. They exercised for 30 minutes on a stationary cycle at a low level of intensity to maximize the use of fat as fuel.
The men took six capsules of a fish oil supplement, two with each of three meals. They ate a meal consisting of 80 percent carbs, 8 percent fat and 12 percent protein 2 1/2 hours before the workout. Since eating that much carbohydrate before exercise is known to block the use of fat as a fuel source, four of the men in the supplement group didn’t eat anything but did take the supplement. There were no differences in fat burning in those who got the fish oil and those who didn’t.
Another study found the same result: no acute effect of fish oil intake on fat oxidation during exercise. That study, however, came to a different conclusion.2 Seven young men (aged 21 to 27), all of whom were actively engaged in both weight training and endurance exercise, were divided into the following groups:
- No meal
- Exercise four hours following a high-fat meal
- Exercise four hours after a high-fat meal in which some of the fat was replaced by a caloric equivalent of fish oil
As with the other study, taking a large dose of fish oil before exercise didn’t affect fat oxidation in the short term. When used for a longer period, however, the fish oil significantly increased the use of fat during exercise. Conclusion: You get better fat loss when you take fish oil supplements long term.
Fish oil aids fat burning because it helps suppress bodyfat synthesis and amplifies fat oxidation in both the liver and muscle. It also lowers malonyl coenzyme-A, a substance produced from carbohydrates that blunts fat burning during exercise. Fish oils stimulate the activity of a gene activator called peroxisomal proliferator-activated receptor-alpha, or PPAR-A, which ignites genes involved in thermogenesis, fatty acid transport and fat oxidation.
A recent study examined the fat-oxidizing effects of EPA, one of two major omega-3 fatty acids.3 Rats were given a high-fat diet that paralleled the kinds of food eaten by obese humans. One group of rats also got supplemental EPA and gained significantly less bodyfat than the unsupplemented rats. The rats on EPA experienced an increase in PPAR-A activity and in apoptosis, or the self-destruction of fat cells. They also had higher levels of adiponectin, an anti-inflammatory substance that favors fat oxidation, as well as decreased tumor necrosis factor-A, an inflammatory. Leptin, still another substance released by fat cells, became normalized in the EPA rats, a metabolic scenario friendly to bodyfat loss.
While some have suggested taking 15 grams or more a day of fish oil for fat loss, the study suggested a daily dose of four grams. Flaxseed oil, which is often listed as a good source of omega-3s, contains alpha linoleic acid, a precursor of DHA and EPA, the active omega-3 fats. Unfortunately, the human body converts only up to 5 percent of ALA into EPA and DHA, making fish oil a far more reliable source of those valuable nutrients.
References
1 Bortolotti, M., et al. (2007). Fish oil supplementation does not alter energy efficiency in healthy males. Clin Nutr. 26(2):225-30.2 Huffman, D.M., et al. (2004). Chronic supplementation with fish oil increases fat oxidation during exercise in young men. J Exerc Physiol Online. 7:48-56.
3 Matute-Perez P. (2007). Eicosapentaenoic acid actions on adiposity and insulin resistance in control and high-fat fed rats: role of apoptosis, adiponectin and tumor necrosis factor-A. Brit J Nutr. 97:389-98.
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